Plural solenoid electromagnetic valve



June 2, 1953 c. c. SHEPPARD 2,640,496

PLURAL SOLENOID ELEcTRon/IAGNET1Cv VALVE Filed Dec. 1948 Patented June2, 1953 PLRAL SOLENOID ELECTROMAGNETIC VALVE Creedy C. Sheppard,Bergeneld, N. J.

Application December 8, 1948, Serial No. 64,139

2 Claims.

This invention relates to an electro-pneumatic control Vsystem and themain object of the invention is to provide pneumatic proportionalcontrol to a process or operation in which the determining factor of theprocess is measured electrically. In the petroleum, chemical and manyyother industries pneumatic control is desired because of its simplicityand to prevent the hazards necessitated by electrical controls in thepresence of vapors and other explosive mixtures. For this reason it isalmost universal to use pneumatic diaphragm valves or other pneumaticmeans for 4regulating the process.

At the same time it is convenient to measure electrically many of thefunctions such as temperature,v humidity, specic gravity which controlthe process. I am aware that many controls now measure electrically andby means of a recorder or other mechanism convert the measurement intopneumatic control. However most of these systems control the pneumaticmechanism by means of a flapper covering an orifice the apper beingactuated by a linkage to the recorder; indicator, or other measuringelement.

yThis type of control is limited by the small motion of the ilapper(usually but a few thousandths of an inch and limited in any event,` toa disltance equal to one-fourth the diameter of the termines thepressure is the difference between the diameter of the orifice and thatof the needle at any given position. The pitch of the needle pointdetermines the amount of motion necessary to produce a given leak area.The shape of the needle determines the relation between motion and leak.A straight cone shaped needle gives a parabolic relation between motionand orifice. A parabolic shaped needle will give a straight linerelation between motion and area. The position of the needle at anygiven moment is determined by a magnetic armature actuated by a coil inwhich the magnetic force is proportional to an electrical measurement ofthe variable.

The position of the needle valve in my invention is determined by thestrength of a magnetic field produced by the electrical measuringelement. It is therefore displaced in proportion to the exciting effectof the measured value-small changes producing a small variation in thecontrol and larger changes a large variation in the control.

One specific application of my invention is illustrated in theaccompanying drawings where- 1n:

Fig. 1 is a diagrammatic view of the improved apparatus.

Fig. 2 is a View upon an enlarged scale showing a portion of theapparatus` in elevation.

This improved apparatus is to regulate the 'specific 'gravity or aprocess in which vtwounlike liquids are to be mixed to produce a desiredspecic gravity. Liquids of different densities are fed to a mixing tankMthrough pipe lines X and Y to produce a desired value of specificgravity in the effluent line Z. For example pipe line X may bedelivering water to the mixing tank and pipe line Y a syrup which mixeswith the water to produce a soft drink having a definite amount of sugaras Ymeasured by its specific gravity regardless of the rates of flow inpipe line X.

To accomplish this a sample `of the resultant liquid is by-passedthrough pipe 5 controlled by valve 5 and allowed to flow into a chamber8, having an overflow wier 9 at its top which maintains a constant levelin the chamber 8. The liquid which overflows from chamber 8 collects inchamber I0 and is drained away to process or waste through a pipe Icontrolled by a valve 'I'. Floating in tank 8 is a hydrometer I I whichwill assume a position determined by the specic gravity of the mixture.The hydrometer is provided with a stem Il which interrupts a light beampassing through shutters I2 and I3 from the light source I4 to thephotocell I5. The amount of light reaching the photocell I5 isdetermined by the height of the float II which in turn is a measure ofthe specific gravity of the sample. Current from photocell I5 isamplified through the amplier tube I6 and passes through the meter I1and the electromagnet I8 having coils I8a, I8b andv IBC. The amount ofcurrent flowing in magnet I8 can be calibrated in terms of the specificgravity of the liquid and will exert a corresponding force on thearmature 2| attracted by the magnet. `The force on the varmature willthen be in proportion to the specilc gravity of the liquid.

. Thecontrol mechanism consists of a supply of air entering through apipe R. controlled by valves RI, R2 and R3 and being reduced to astandard pressure indicated on gauge Gl, say pounds, by action of thereducing valve Rl. This pressure then is restricted as to its flowthrough variable reducing valve R2 the pressure being indicated on dialG2. The pressure shown on dial G2 is the resultant of the iiow throughvalve R2 and the amount which leaked oi through loriice 23, the amountof leak fbeing determined 'by 'the 'position of :needle valve U22 Whichis in turn controlled through the armature 2| by the current iiowingthrough the electromagnet i8. If no current flows through the magnet theneedle valve will rest against the stop 24. iiows through magnet I8 theneedlevalve :22 will enter the lower end of orifice 23 and close itcompletely, in which case the pressure Lwill build up until that shownon the dial G2 fequals fthe pressure shown on dial Gl.

Since the position of the needle valve is -de termined by thearmature'nux it is 'quite possible to take into account 'a number 'difactors in determining the .unal flux. In the pneumatic control art itis current practice to have features in the device to anticipate theVaction of the control due to sudden change in the variables, tomodulate it according to the rate of change, and the like.

In my apparatus themagnet l thas three separate coils 18a, I8b,'andi`8'c. Coil 18a determines the magnetism contributed by .the position ofthe iioat Ii and coil [8b receives an impulse from an electric flowmeter F 'connected with this coil by Wires F and associated with thepipe v X. A sudden change inthe rate 4of 'flow'cancause too great animpulse and anticipate its effect in the mixing tank 'also asserting acorresponding force on the arm'ature'l. HIn'the mixing tank itself thereactions 'or `the resultsniayI be iniiuenced by temperature. 'ThereforeI place Vin the tank M a temperature device'T which gives an electricalimpulse and is connected 'with vco'il 'lac by wires AT and causing theiluxlto `b'e modi- 'fied according to 2this factor.

ing the magnetic nux.

The magnetic iiux produced "by coil lB-a may 'be either increased ordecreased "by the current iiowing Jin coil |811 depending upon thedirection it passes through the coil. It will then add or subtractmagnetic force acting on 'the armature to produce a change .induced:bythe electrical measurements 'of a second variable in the process.

Y. This Valve may "be adjusted from a fully opened position toa'position in l`which vitis fully -closed according `'to :the pressureshown upon `the gauge G2. The electrical Acurrent "in magnet i8 will,therefore, determine pressure in the gauge G2 `and the correspondingposition-oi Lvalve D. The position of the `needle'valve A22 isdetermined by'three forces acting 'on it; lthe tension of spring T9,'andthe `pressure in the Isystem as indicated by the gauge LG2 acting onthe area of the needle 'valve 'tending to tilt "the On the other hand ifsuiicient current'l Accordingly 'the resultant position of the armatureand the needle valve will be determined by the three modify- 4 armaturein a clockwise direction and magnetic pull of magnet i8 tending tooperate it in a counterclockwise direction. Each of these three forceshas its own leverage action indicated as a, b, and c in Figure 2 which,multiplied by its force equals the moments acting on the armature.

The sum of the moments constitutes the force balance, and :needle valve`22 will assume a position to reduce f-this sum to zero, thus .iixingthe position to produce proper operating pressure in diaphragm motor Dto hold the process steady at the set point until one or" the variableschanges. A change inthe velectrical measurement of one of the variableproduces a change in magnetism .Ourthe armature, and a new balancepoint. Since the changes in current will be in proportion to thedeviation in the set point, the device will function as a proportionalcontroller. Further, since the size of the orice and the slope, or areaof the needle valve for any given position, may be designed to give wideranges and fine sensitivities to control mechanisms not possible withthe flapper mechanism whose total motion is limited to one-fourth thediameter of 'the oriice and whose major regulation is confined to astill smaller range. A still furtheradvantage is that by making theneedle valves and orice jets interchangeable parts in the c ontrolmechanism by merely substituting a .piston needle valve and orifice, thecontrol Acan be quickly changed to an entirely diierent range and.sensiti'vity. In a plant using large numbers of controllers, thispermits standardization on 4a relative simple .and inexpensive mechanismfor -most control problems, each being adapted'to its particular job byinserting proper needle valjvepiston and orice.`

Further, the eiiective Vforce of 'the magnetic pull for any givencurrent can be varied by changing the air gap d vbetween the armatureand the pole piece of the magnet. This lis accomplished by verticallyshifting the vbracket '2B which carries the orifice with respect .toVAthe bracket 3l Vcarrying the .coil f8 by Vmeans .of the eccentric '28after loosening the securing screws 2l.

A spring 35 is introduced between the bracket 29 and the bracket 4:iland serves to separate them to the limit permitted by the eccentric 2'8.It is only necessary, then, to rotate '2li to produce any desired gap dbetween the armature "2l and the yoke. It is therefore, possible topr'oduce equilibrium in the system at any desired value of current inthe magnet f8 and consequently at any desired specic gravity of 'themixed liquid. 'When this equilibrium is disturbed, by a change ingravity the valve `l3`=wil1 'be 'iniiuenced to .regulate vthe flow inthe pipe line Y and to restore the gravityto the set puin't. Furthermorethe ve'iect of the pressure vonth'e diaphragm of the valve D will be in'proportion to the variation in coil current (and therefore of specificgravity) from the set point, a 'smal'l 'change producing asmall'corrective actionland a correspondingly large 'corrective vaction.

It is to be noted that the action of the -magnet and the armature Vinthe system I have perfected differs materially from that of theconventional electric relay. In the "latter Acase 'van increase ofcurrent causes motion 'of Vthe carniature towards the yoke andas thearmature *nears the yoke :the magnetic -gap rbeing'lowered'the pull of`the magnet is increased, the ie'iiective 'torce being inverselyproportional to Ithe square of the distance across the air gap. Thiseffect causes the characteristic action of the electrical relay whichhas two definite values called the pull in and drop out points givingthe desired snap action.

In my device an increase in current through the coil 18e of the magnetI8 acting through its lever arm b moves the needle valve 22 andrestricting the orifice builds up the pressure determined by the leak.This pressure acting through the lever arm c opposes the motion of thearmature thus replacing the snap action of an ordinary electrical relaywith a true iioating action depending on the magnetic pull of the magnetacting through its lever arm b and the pressure acting through its leverarm. By suitably adjusting the spring tension and the air gap theequilibrium point can be set any desired value between full pressure andcomplete leak off or zero pressure.

Furthermore any disturbance of this set pressure will bring into playforces in proportion to the disturbance tending to restore the set'pressure, in other words automatic control of the process, tending tomaintain the output at any desired set value. The sensitivity of theresponse can be controlled by regulating the needle valve R2 and if onlya small leak is permitted here obviously a small change in leak throughorice 23 will produce a large change in the pressure shown by G2. On theother hand if a greater ilow is permitted through valve R2 it will takea correspondingly larger motion of needle valve 22 to establish thepressure.

To overcome objectionable hunting of the controlled valve above andbelow the set point I have provided another needle valve R3 mountedinthe 'portion of the pipe line R leading to a reservoir or airreceiver. By means of this valve R3 the rate of iiow into and out of theair receiver can be regulated. If we assume that the operating pressuregauge GI is pounds and the set pressure to provide proper specificgravity is 9 pounds the system Will balance at a point in which the leakoff at valve 22 will become 9 pounds and this pressure will be presenton the diaphragm of valve D and also in the air receiver and the wholesystem will be at rest as long as the specific gravity corresponds tothe set point giving a pressure of 9 pounds.

Now suppose the specic gravity goes up lifting the float Il and therebycutting down current in coil 18a and permitting more air to escape atorifice 23 by movement of needle Valve 22 and reducing pressure ondiaphragm valve D thus cutting down the now of liquid Y and reducing thespeciiic gravity, it being assumed that liquid Y is heavier than liquidX. At this point as the air pressure is reduced air from the receiverwill flow into the system tending to prevent the pressure falling toofast in valve D and thus causing it to overshoot the set point and huntThe pressure resulting from leak at 22 is made up of two parts; onecoming through valve R2 from the air supply and the other coming fromthe air stored in receiver and escaping through valve R3. By adjustingthe valve R3 the amount of this corrective action or reset action can bevaried to suit the particular limits and sensitivity desired in theapparatus. On the other hand if needle valve 22 moves to increase thepressure in the system,

part of the eiect is felt at the diaphragm valve D and part of the eiectis used to store up pressure in the air receiver. The action of thisreceiver or reset action is very much like a storage battery oating onan electrical line to absorb changes in voltage and smooth them out.

I have thus provided an apparatus for electrically measuring the endproduct o a process;

any process, and not necessarily the specificing a vertically disposedchamber having an inllet at its top and an outlet aperture at itsbottom, a needle valve under said chamber shiftable vertically into andout of said aperture, an electro-magnet disposed vertically adjacent oneside of said chamber and having upper and lower and intermediatepositions provided with separate windings adapted to be independentlyenergized, an armature bar extending horizontally under saidelectroniagnet, said armature bar being pivotally mounted outwardly ofthe electromagnet and having its inner end extending under the chamberand carrying said needle valve, said armature being pivotally mounted inspaced relation to the outer end, a spring urging the outer end of saidarmature upwardly and yielduably holding the armature away from themagnet at a downward incline towards its inner end, and an abutmentunder the inner end of the armature limiting downward movement of thearmature and the needle valve and being shiftable vertically to adjustedpositions.

2. The structure of claim 1 wherein the chamber is carried by a bracketshiftable vertically to adjust the chamber relative to the electromagnetand the abutment consists of a screw threaded upwardly through anopening formed in platform projecting forwardly from the bracket.

CREEDY C. SHEPPARD.

References Cited in the le of this patent UNITED STATES PATENTS NumberName Date 932,940 Allen Aug. 31, 1909 1,008,201 Schmucker Nov. '7, 19111,210,180 Logan Dec. 26, 1916 1,664,840 Wermine Apr. 3, 1928 1,758,450Machlet May 13, 1930 1,925,833 French Sept. 5, 1933 1,949,685 Hume Mar.6, 1934 1,951,035 Parker Mar. 13, 1934 1,989,829 Specht Feb. 5, 19352,171,312 Meyers Aug. 29, 1939 2,310,298 Kuhl Feb. 9, 1943 2,382,853Brammer Aug. 14, 1945 2,523,198 Davies Sept. 19, 1950 FOREIGN PATENTSNumber Country Date 839,703 France of 1939

